第十章 神经系统的功能与麻醉

【目的要求】了解神经元和神经胶质细胞的一般功能，反射活动的基本规律，神经元间相互作用的方式，中枢递质，躯体运动的概念和分类，基底神经节和大脑皮质对躯体运动的调控，本能行为和情绪的神经调控，皮层诱发电位，觉醒。熟悉兴奋在反射弧中枢部分传播的特征，大脑皮层的感觉功能，脑干对肌紧张和姿势的调控，脑电图，脑的高级功能。掌握突触传递机制和特征，外周神经递质和受体的分类、分布及作用，突触后抑制的分类、概念和意义，丘脑的感觉投射系统，脊髓对躯体运动的调节，小脑的运动调节功能，自主神经系统的功能和特征，下丘脑对内脏活动的调节，睡眠的时相、特点和意义。掌握意识的概念，意识产生的机制及意识的特性。了解疼痛的概念及生物学意义，疼痛的分类及特点，疼痛的测定与评估。掌握疼痛产生的机制及麻醉镇痛和镇痛机理。掌握麻醉与植物神经系统的功能。

【教学内容】

1.        神经元的一般结构和功能，神经纤维及其功能，神经的营养性作用，神经胶质细胞的特征和功能。

2.        突触的概念、分类。经典突触传递过程、递质释放的机制、特点及影响因素，兴奋性和抑制性突触后电位。非定向突触和电突触。递质和调质和概念，递质共存现象，受体的概念、亚型和调节，乙酰胆碱及其受体、去甲肾上腺素及其受体分布及其作用。

3.        反射的分类和中枢整合，中枢神经元的联系方式，局部回路神经元和局部神经元回路，中枢兴奋传播的特征，突触后抑制（传入侧支抑制和回返抑制）分类及作用和突触前抑制，中枢易化。麻醉深度与反射活动：眨眼反射、眼睑反射、皮肤反射、咽反射、腹膜反射、喉反射、瞳孔对光反射。麻醉深浅的判断指征。

4.        躯体感觉传导通路，丘脑的感觉特异投射系统与非特异投射系统，大脑皮层的感觉代表区，中枢对内脏感觉的分析功能。疼痛的概念、分类及特点。疼痛产生机制，麻醉镇痛及其镇痛机理。

5.        运动的分类及中枢调控系统，脊休克，运动神经元与运动单位，牵张反射的概念、分类、作用和产生过程，肌梭与腱器官。屈肌反射、对侧伸肌反射和节间反射。脑干对肌紧张和姿势的调节，小脑的运动调节功能，基底神经节和大脑皮层对运动的调控。局麻药对躯体运动的影响，肌松药对肌肉张力的影响。

2.        自主神经系统的结构和功能特征以及功能。自主物神经系统兴奋传递的递质与受体：胆碱能纤维与受体、肾上腺能纤维与受体。脊髓、低位脑干、下丘脑和大脑皮层对内脏活动的调节，本能行为和情绪活动的神经基础，动机与成瘾。麻醉与内脏的反射活动：循环系统的反射、呼吸系统的反射、呕吐反射。

3.        正常脑电图和脑诱发电位的基本波形及出现条件、形成机制。睡眠的时相、特点和生理意义，与觉醒和睡眠有关的脑区和调节物质。

4.        学习的形式，非条件反射与条件反射，记忆的形式和过程，遗忘，学习和记忆的机制。大脑皮层的一侧优势和语言中枢，大脑皮层的其他认知功能和两侧大脑皮层功能的相关。

5.   意识的概念，产生的机制及特性。正常意识与意识障碍。

【计划学时】20学时。

Chapter X Nerve System

   The nervous system is divisible into a central component, consisting of the brain and spinal cord, and a peripheral component, consisting of nerve axons, dorsal root ganglia, and autonomic ganglia. The brain is divisible into: the brainstem (made up of the pons, medulla, and midbrain), the cerebellum, the diencephalon (made up of the thalamus and hypothalamus), and telencephalon (cerebral hemispheres). In the central nervous system, regions containing cell bodies are gray matter; those consisting of axons are white matter.

Functional Anatomy of Neurons

  The basic unit of the nervous system is the nerve cell, or neuron. Dendrites and the cell body receive information from other neurons. The axon (nerve fiber), which may be covered with sections of myelin separated by nodes of Ranvier, transmits information to other neurons or effector cells.

  Neurons are classified in three ways: Afferent neurons transmit information into the CNS from receptors at their peripheral endings. Efferent neurons transmit information out of the CNS to effector cells. Interneurons lie entirely with the CNS and connect afferent and efferent neurons. Information is transmitted across a synapse by a neurotransmitter, which is released by a presynaptic neuron and combines with receptors on a postsynaptic neuron. The CNS also contains glial cells, which sustain the neurons metabolically, form myelin, and serve as guides for the neurons during development.

Signal Transduction of Synapses

  The signal from a pre- to a postsynaptic neuron is a neurotransmitter stored in synaptic vesicles in the presynaptic axon terminal and released into the synaptic cleft when the axon terminal is depolarized, thereby raising the calcium concentration within the terminal.

   Depolarization of the synaptic terminal leads to an influx of Ca++, stimulating fusion of transmitter vesicles with the presynaptic membrane. Some of the neurotransmitter release and diffuses to the postsynaptic cell and are bound by receptor molecules on its surface. Receptor binding activates ion channels directly or by way of a G protein, leading to a change in the membrane conductance and a postsynaptic potential. The postsynaptic potential may summate with other synaptic inputs to increase or decrease the probability of an action potential in the postsynaptic cell. Excitatory (depolarizing) postsynaptic potentials result from an increase in conductance to all small cations; inhibitory postsynaptic potentials may be hyperpolarizing (resulting from an increase in K+ conductance) or silent (resulting from an increase in CL- conductance that stabilizes the membrane potential near its resting value). If the synapse is on another synaptic terminal, it can influence the synaptic efficacy of the second synapse, either increasing it (presynaptic facilitation) or decreasing it (presynaptic inhibition). Arrangement of neurons into circuits with appropriate synaptic connections makes the activity of postsynaptic cells depend on the inputs they get from presynaptic cells; this is the basis of neural integration in the nervous system.

  The neurotransmitter diffuses across the synaptic cleft and binds to receptors on the postsynaptic cell, where they usually open ion channels. At an excitatory synapse the electrical response in the postsynaptic cell is called an excitatory postsynaptic potential (EPSP). At an inhibitory synapse, it is an inhibitory postsynaptic potential (IPSP). Usually at an excitatory synapse, channels in the post-synaptic cell that are permeable to sodium, potassium and other small positive ions are opened; whereas at inhibitory synapses, channels to potassium and/or chloride are pened .The postsynaptic cell's membrane potential is the result of temporal and spatial summation of the EPSP and IPSP at the many active excitatory and inhibitory synapses on the cell.

  Neuroeffector Communication The junction between a neuron and an effector cell is called a neuroeffector junction. The events at a neuroeffector junction release of transmitter into an extracellular space, diffusion of transmitter to the effector cell, and binding with a receptor on the effector cell are similar to those at a synapse.

  Receptor Receptors translate information from the external world and internal environment into graded potentials, which then generate action potentials. Receptors may be either specialized endings of afferent neurons or separate cells adjacent to the neurons. Receptors respond best to one form of stimulus energy, but they may respond to other energy forms if the stimulus intensity is abnormally high. Regardless of how a specific receptor is stimulated, activation of that receptor always leads to perception of one sensation. Application of a stimulus to a receptor opens ion channels in the receptor membrane. Ions then flow across the membrane, causing a receptor potential. Receptor potential magnitude and action potential frequency increase as stimulus strength increases. Receptor potentials can be summed.

Somatic Sensation

  Sensory function of the skin and underlying tissues is served by a variety of receptors sensitive to one (or a few) stimulus types. Information about somatic sensation enters both specific and nonspecific ascending pathways. The specific pathways cross to the opposite side of the brain. The somatic sensations include touch-pressure, proprioception and kinesthesia, temperature, and pain. Some mechanoreceptors of the skin are rapidly adapting and give rise to sensations such as vibration, touch, movement, and tickle, whereas others are slowly adapting and give rise to the sensation of pressure. Skin receptors having small receptive fields are involved in fine spatial discrimination, whereas receptors having larger receptive fields signal less precise touch/pressure sensations. The major receptor type responsible for proprioception and kinesthesia is the muscle-spindle stretch receptor. Cold receptors are sensitive to decreasing temperatures; warm receptors signal information about increasing temperature. Specific receptors give rise to the sensation of pain, which may induce emotional and reflex responses as well as the perception of pain. Stimulation-produced analgesia and TENS control pain by blocking transmission in the pain pathways. Temperature and pain are sensed by free nerve endings. The dorsal columns of the spinal cord are labeled lines that carry sensory pathways to specific cortical processing regions. The nonspecific pathway exercises a general arousal effect on the brain by way of the reticular activating system.

  Neural pathways in sensation A single afferent neuron with all its receptor endings is a sensory unit. The area of the body that, when stimulated, causes activity in a sensory unit or other neuron in the afferent pathway is called the receptive field for that neuron. The specific ascending pathways convey information about only a single type of information to the cerebral cortex. Nonspecific ascending pathways convey information from more than one type of sensory unit to the brainstem reticular formation and regions of the thalamus not part of the specific ascending pathways.

Regulation of Motor Function

  The neural systems that control body movements are arranged in a motor control hierarchy. The highest level determines the general intention of an action. The middle level specifies the postures and movements needed to carry out the intended action and, taking account of sensory information that indicates the body's position, establishes a motor program. The lowest level determines which motor neurons will be activated. As the movement progresses, information about what the muscles are doing is fed back to the motor control centers, which make any needed program corrections. Actions are voluntary when we are aware of what we are doing and why or when we are paying attention to the action or its purpose. Almost all actions have conscious and unconscious components.

  Local control of motor neurons Somatic motor neurons project directly to skeletal muscle fibers, innervating each muscle fiber with a single excitatory synapse. Most input to motor neurons arises from local interneurons, which themselves receive input from peripheral receptors, descending pathways, and other interneurons. Muscle length and changes in length are monitored by muscle spindle stretch receptors. Activation of these receptors initiates the stretch reflex, in which motor neurons of ipsilateral antagonists are inhibited and those of synergists are activated. Tension on the stretch receptors is maintained during muscle contraction by gamma efferent activation of the spindle muscle fibers. Alpha and gamma motor neurons are often coactivated. Muscle tension is monitored by Golgi tendon organs, which inhibit motor neurons of the contracting muscle and stimulate ipsilateral antagonists. The flexion reflex excites the ipsilateral flexor muscles and inhibits the ipsilateral extensors. The crossed-extensor reflex excites the contralateral extensor muscles during excitation of the ipsilateral flexors.

  Spinal segmental reflexes that contribute to posture, protection, and voluntary movement include (1) the stretch reflex, which maintains muscle length constant; (2) the withdrawal reflex, which mediates rapid flexion of an injured limb; (3) the crossed extension reflex, which extends the limb contralateral to a flexed limb; and (4) the Golgi tendon reflex, which may protect muscles and their tendons from extremes of tension.

   Motor programs may be generated at several levels in the central nervous system. Simple stepping can be carried out by the spinal cord. More complicated motor programs require the participation of the basal ganglia, motor cortex, and cerebellum. The cell bodies of motor neurons in spinal cord segments are arranged so that distal muscles are served by lateral motor neurons and medial motor neurons control proximal muscles. Pathways from the motor centers of the brain to spinal motor neurons can be divided roughly into two categories: one class that serves primarily proximal muscles and mainly mediates adjustments of posture, and one that serves distal muscles and is important for fine movements. Control of distal muscles is exerted mainly by the direct corticospinal (pyramidal) tract; control of proximal muscles involves polysynaptic (extrapyramidal) tracts that pass through brainstem nuclei.

  Descending pathways and the brain centers that control them The location of the neurons in motor cortex varies with the part of the body the neurons serve. A readiness potential is fired from the supplementary motor area 800 ms. before any electrical activity in motor cortex begins. This is followed by a motor potential in motor cortex. The basal ganglia help determine the direction, force, and speed of movements. The cerebellum coordinates posture and movement. The pathways pass directly from the sensorimotor cortex to motor neurons in the corticospinal spinal cord (in the brainstem, in the case of the corticobulbar pathways) or to interneurons near the motor neurons. In general, neurons on one side of the brain control muscles on the other side of the body. Corticospinal pathways serve predominantly fine, precise movements. Some corticospinal fibers affect the transmission of information in afferent pathways. The multineuronal pathways consist of chains of neurons that carry information from the sensorimotor cortex, basal ganglia and other subcortical nuclei, cerebellum, and brainstem nuclei to motor neurons in the brainstem or spinal cord or interneurons near them. Some fibers loop back to alter earlier pathway components. The multineuronal pathways are involved in the coordination of large groups of muscles used in posture and locomotion. There is some duplication of function between the two descending pathways.

  Muscle tone Muscle tone is due to the viscoelastic properties of muscles and joints and to any ongoing contractile activity.

  Maintenance of upright posture and balance To maintain balance, the body's center of gravity must be maintained over the body's base. Postural reflexes depend on inputs from eyes, vestibular apparatus, and proprioceptors. The stretch and crossed extensor reflexes are postural reflexes.

Functions of Autonomic Nervous System

The preganglionic neurons whose cell bodies are in the central nervous system synapse in peripheral ganglia with postganglionic fibers that innervate visceral effectors. The parasympathetic and sympathetic branches of the autonomic motor system differ anatomically in that the ganglia in the sympathetic branch are anatomically remote from the effector organs, while the ganglia of the parasympathetic branch are located in or on the effector organs. Visceral effectors typically have dual innervation by autonomic fibers from both the sympathetic and parasympathetic branches and may possess more than one motor synapse on each effector cell. As a general rule of organization of the motor systems, the transmitter chemical at the first synapse outside the nervous system is acetylcholine.

The responses of visceral effectors to autonomic inputs are mediated by pharmacologically distinguishable types of receptor molecules. Nicotinic cholinergic receptors are located on autonomic postganglionic cells of both branches, but muscarinic receptors are found on effectors innervated by cholinergic postganglionic fibers. Adrenergic receptors are divided into a and B types, and into a1, a2, B1and B2 subtypes. The subtypes are typically associated with particular effectors, although some effectors have more than one subtype. For any given tissue, the effect of autonomic inputs depends entirely on the second messenger systems activated by transmitter-receptor binding; the same receptor subtypes can frequently mediate opposite responses in different tissues.

States of Consciousness and Emotion

  States and experiences of consciousness Electric currents in the cerebral cortex due predominately to summed postsynaptic potentials are recorded as the EEC. Slower EEG waves correlate with less responsive behaviors. Rhythm generators in the thalamus are probably responsible for the wavelike nature of the EEG. Alpha rhythms and, during EEG arousal, beta rhythms characterize the EEG of an awake person. Sleep is an activity of the brain. It can be divided into slow-wave sleep and REM sleep on the basis of differences in the EEC, muscle tone, and arousability .Slow-wave sleep progresses from stage I (faster, lower-amplitude waves) through stage 4 (slower, higher-amplitude waves), followed by an episode of REM (paradoxical) sleep. There are generally five of these cycles per night .In the brainstem, a sleep producing system and an arousal system interact to produce sleep-wake cycles. Brain structures involved in directed attention, particularly the locus ceruleus, are thought to determine which areas of the brain gain temporary predominance in the ongoing stream of conscious experience. It is believed that conscious experiences, which depend on directed attention, occur because of activity in interacting neuron networks. In order for conscious experiences to occur, neural activity must be present in the brain for a minimum period of time. Neural processes that result in perceptions, judgments, problem solving ability, and discriminative responses to stimuli can occur even though conscious experiences do not develop.

  Emotion Behaviors that satisfy homeostatic needs are primary motivated behaviors. Behavior not related to homeostasis is a result of secondary motivation. Repetition of a behavior indicates appetitive motivation. Avoidance of a behavior indicates aversive motivation. Lateral portions of the hypothalamus are involved in appetitive motivation. Norepinephrine, dopamine, and enkephalin are transmitters in the brain pathways that mediate appetitive motivation and reward. Two aspects of emotion, inner emotions and emotional behavior, can be distinguished. Different brain areas mediate these two aspects of emotion, but both aspects work together so that the behaviors truly represent the inner emotions. The limbic system integrates inner emotions and behavior.

Learning and Memory

   Motivations (rewards and punishments) are generally crucial to learning. Working memory has limited capacity, is short term, and depends on functioning brain electrical activity. After registering in working memory, facts either fade away or are consolidated in long-term memory, depending on attention, motivation, and various hormones. Long-term memory, of which there are two forms procedural and declarative seems to have an unlimited capacity and to be independent of brain electrical activity. Memory traces are localized, discrete brain areas containing cellular or molecular changes specific to different memories. Learning is enhanced after subjects are exposed to enriched environments. The enhancement is presumably due to the brain neural and chemical development that follows such exposure. Learning occurs when sensory inputs result in altered behavior. The behavior alteration may involve responses to repeated stimuli (habituation and sensitization) or induction of a response to a neutral stimulus (associative learning). Information may be stored in verbal and nonverbal forms, and it is not possible to identify a single discrete brain region in which memory stores are located. Short-term memory depends on electrical activity in neuronal circuits. In simple nervous systems, long-term storage appears to involve a change in synaptic responsiveness that requires protein synthesis. In the course of development, the dominant hemisphere differentiates a specialization for control of voluntary motor activities and language. Usually the left hemisphere becomes dominant.       The non-dominant hemisphere differentiates a specialization for nonverbal intellectual functions. Damage to language regions of the dominant hemisphere results in aphasias (language disabilities) and impairments of verbal memory. Damage to corresponding regions of the nondominant hemisphere results in impairment of spatial and nonverbal functions.

Cerebral Dominance and Language

The two cerebral hemispheres differ anatomically, chemically, and functionally. In 90 percent of the population, the left hemisphere is superior at producing language and in performing other tasks that require rapid changes over time.

内容提要

（一）神经系统是对体内功能起主导调节的系统。

神经元是神经系统的基本结构和功能单位，由胞体和突起两部分组成。神经纤维的主要功能是传导兴奋，神经纤维在传导兴奋的过程中具有以下的特征：①生理完整性②相对绝缘性③双向性④相对不疲劳性。

突触是神经元之间的功能接触部位，包括兴奋性突触和抑制性突触两种。突触前膜释放的是兴奋性递质，递质经突触间隙扩散，同突触后膜上的特异性受体结合，后膜对Na⁺、K⁺和Cl^-通透性↑，以Na⁺内流为主，使后膜产生去极化。这种去极化性的电位称为兴奋性突触后电位（EPSP）。突触前膜释放的是抑制性递质，递质经突触间隙扩散，同突触后膜上的特异性受体结合后，后膜对Cl^-和K⁺通透性↑，Cl^-内流和K⁺外流（以Cl^-内流为主），使突触后膜产生超极化。这种超极化电位变化称为抑制性突触后电位（IPSP）。这两种突触后电位均具有局部电位性质。

（二）中枢神经系统调节机体活动的基本方式是反射。

兴奋经突触传递的特征包括单向传递、中枢延搁、总和、兴奋节律的变化、后发放及对内环境变化的敏感性和易疲劳性等。中枢神经系统的基本活动过程包括兴奋和抑制。中枢抑制包括突触前抑制和突触后抑制。某神经元兴奋一个抑制性中间神经元，后者释放抑制性递质，使与其发生联系的突触后神经元产生IPSP，从而使突触后神经元发生抑制，称为突触后抑制。由于突触前膜释放兴奋性递质减少而引起突触后膜兴奋程度下降（抑制），称为突触前抑制。中枢神经元间的联系主要有辐散式、聚合式、环式和链锁式等几种方式。

（三）神经系统对感觉的调节

1.感受器感觉形成的外周机制

通过各感觉中枢的分析、处理和整合后产生相应的感觉或意识，同时还可产生各种反射活动。体内有的感受器活动并不使个体在主观上产生特定的感觉，而是向有关中枢提供环境中某些因素变化的信息，进而引起相应的调节反应。

感受器的作用是接受刺激。每种感受器都有其适宜的刺激，并在接受刺激后，通过其换能和编码的功能，将刺激的信息转换为传入神经上的动作电位，且在接受刺激的过程中表现出适应的现象。①每种感受器通常只对某种特定形式的能量变化敏感，这种形式的刺激称为该感受器的适宜刺激。②感受器能将不同的刺激能量转换为传入神经上的动作电位的过程，称为感受器的换能作用。③感受器在进行换能作用的同时，还把刺激的部位、性质、强度、速度和时间等信息也同时转移到传入神经的动作电位序列中，这一过程称为感受器的编码作用。④当恒定强度的刺激持续作用于感受器时，其传入神经上的动作电位频率会逐渐下降，这一现象称为感受器的适应。

2.感觉形成的中枢机制

（1）脊髓的感觉传导与分析功能

浅感觉传导路径:痛觉、温度觉和轻触觉→后根后角换元→交叉对侧→脊髓丘脑侧束（痛、温觉）和脊髓丘脑前束（轻触觉）→丘脑.

深感觉传导路径: 后根的内侧部→同侧后索→抵达延髓下部薄束核和楔束核换元→交叉到对侧→经内侧丘系至丘脑。

(2)丘脑的感觉投射系统

丘脑不同核群的功能特征将其分为3类。①感觉接替核，这一类核团是各种特异感觉传导途径的中继站丘脑是重要的感觉接替站，能对感觉传入信息进行粗略分析和综合②联络核，接受特异性核群和其他皮质下中枢来的纤维，换元后投射到大脑皮层的特定区域，参与调节躯体和内脏活动以及各种感觉功能的相互联系和协调③非特异性核群，是指靠近中线的内髓板以内的各种结构。

感觉投射系统分为特异性投射系统及非特异性投射系统，前者的功能是引起特定的感觉并激发大脑皮层产生传出神经冲动；后者的功能是维持和改变大脑皮层的兴奋状态，不引起特定的感觉。非特异性投射系统是特异性投射系统功能的基础。中央后回是大脑皮层感觉区。特异性和非特异性投射系统的结构和功能特征比较

（3）大脑皮层的感觉功能

大脑皮层是感觉分析的最后和最高级的部位。各种感觉传入冲动最终都到达大脑皮层，在此进行信息的加工和整合，最后形成感觉和意识。

3.痛觉

痛觉（pain sensation）是机体受到伤害性刺激后产生的不愉快的主观体验。

（1）躯体痛体表痛和深部痛。包括发生在体表某处的痛称为体表痛。具有“双重痛感”。 快痛是出现快消失也快，定位清楚的刺痛；慢痛是一种定位不明确的烧灼痛，伴有情绪反应和心血管、呼吸等方面的变化。发生在骨、关节、骨膜、肌腱、韧带和肌等处的痛称为深部痛。其特点是定位不明确，可伴有恶心、出汗和血压改变等自主神经反应。

（2）内脏痛（visceral pain）是由胸腹腔脏器病变引起的疼痛。呈灼痛或钝痛，发生较慢，持续时间较长，痛区的边缘难以确定，常伴有自主性反应和神经-精神性反应。

（3）牵涉痛（referred pain）是内脏疾病引起的体表某些部位发生疼痛或痛觉过敏的现象称为牵涉痛。

（四）神经系统对姿势和运动的调节

骨骼肌的肌紧张是维持机体姿势的基础，机体的任何运动都是在一定的姿势和肌紧张的条件下进行的。姿势和运动是互相联系的。姿势是一切运动的起点和终点。

1.脊髓对运动的调节

是脊髓运动反射的最后公路。由一个α神经元所支配的全部肌纤维所构成的一个功能单位，称为运动单位(motor unit)。高位中枢离断的脊髓，暂时丧失反射活动的能力，进入无反应状态，称为脊休克。脊休克的产生与恢复说明脊髓能完成简单的反射活动，但正常时是在高位中枢的调节下活动的。

（1）牵张反射 牵张反射有位相性牵张反射和紧张性牵张反射两种类型。

1)位相性牵张反射，指快速牵拉肌腱时发生的牵张反射,又称为腱反射(tendon reflex)，表现为骨骼肌的一次快速收缩和舒张，使机体原有的姿势得以维持。

2)紧张性牵张反射 指骨骼肌受到缓慢持续牵拉时发生的牵张反射，又称为肌紧张(muscle tonus)，表现为受牵拉的肌发生紧张性收缩以阻止被拉长。

反射过程：在骨骼肌受到突然的外力牵拉而伸长时，肌梭感受器受刺激而兴奋，冲动经Ⅰa和Ⅱ类纤维传入脊髓，使脊髓前角支配该肌的和同一关节协同肌的α神经元兴奋（通过抑制性中间神经元的作用，使支配对抗肌的α神经元抑制），α神经元传出冲动增多，梭外肌收缩，长度缩短，以对抗外力的牵拉，使机体的姿势得以保持。

（2）屈肌反射和对侧伸肌反射

当肢体受到伤害性刺激性，引起受刺激一侧的肢体屈肌收缩，肢体屈曲称屈肌反射。具保护意义。当伤害性刺激较强时，在同侧肢体屈曲的同时，对侧肢体出现伸直的反射，有维持姿势的意义。

2.低位脑干对运动的调节

（1）脑干网状结构对肌紧张的调节

延髓网状结构腹内侧区域，对反射性运动和刺激皮质诱发的运动都有抑制作用，基于该区域有抑制肌紧张和运动的功能，故称为抑制区。延髓网状结构背外侧、脑桥和中脑被盖区域，对反射性运动和刺激皮质引起的运动都有加强作用，由于该区域有加强肌紧张和运动的功能，故称为易化区。

脑干网状结构易化系统和抑制系统在调节全身骨骼肌的紧张性和完成各种运动的过程中具有重要作用。正常情况下，易化系统的活动强度略大于抑制系统。实验条件下，在猫的中脑上、下丘之间切断，使易化区的活动更加增强，动物表现去大脑僵直。

3.小脑对运动的调节

小脑通过同大脑皮层、丘脑、脑干网状结构、红核、前庭核和脊髓等保持广泛的联系，同时接受来自骨骼肌、关节等与运动直接有关的感受器以及视觉和听觉的传入冲动，而具有参与运动设计和运动的执行，协调各运动中枢活动，维持身体平衡、调节肌紧张和协调随意运动等功能。（1）前庭小脑主要由绒球小结叶构成，主要功能是维持躯体的平衡和眼球的运动。绒球小结叶受损的个体，出现平衡失调综合征（dysequilibrium syndrome）。（2）脊髓小脑由蚓部和半球中间部组成，主要功能是调节肌紧张和正在进行过程中的运动，协助大脑皮层对随意运动的控制。小脑对肌紧张的调节具有抑制和易化双重作用，分别通过脑干网状结构抑制区和易化区而发挥作用。脊髓小脑受损后，表现为意向性震颤和共济失调。（3）皮层小脑指后叶的外侧部。通过对大脑皮层下传的信息和肌运动变化的上传信息进行比较，以调整和纠正有关肌群的活动水平，使机体的随意运动保持协调。

4.基底神经节对运动的调节

基底神经节（basal ganglia）是皮质下一些核团的总称，包括尾状核、壳核、苍白球、丘脑底核、黑质和红核。

基底神经节同大脑皮层间和在其内部核群间形成的环路联系，参与对肌紧张的控制和随意运动稳定的调节。

基底神经节损害的临床症状主要是运动功能障碍，表现为：①运动过少而肌紧张过强，如帕金森病（震颤麻痹）②运动过多而肌紧张不全，如亨廷顿病（舞蹈病）。

5.大脑皮层对运动的调节

大脑皮层是调节随意运动的中枢。包括中央前回、运动前区、运动辅助区和后部顶叶皮质等区域。大脑皮层运动区细胞呈纵向柱状排列，组成大脑皮层的基本功能单位，称为运动柱。

(1)支配特点：①对躯体运动的调节支配具有交叉的性质②具有精细的功能定位③运动区的分布呈身体的倒影（头面部代表区内部的安排仍为正立而不倒置）。

(2)皮质传导束包括皮质脊髓束和皮质核束

①由皮质发出后经内囊、脑干下行到达脊髓前角α和γ运动神经元的传导束，为皮质脊髓束。皮质运动区发起的随意运动，通过皮质脊髓束控制脊髓的α和γ神经元的兴奋性以调节肌的活动；通过中间神经元的联系以保持对抗肌运动神经元之间的活动平衡，使肢体活动具有合适的强度，以维持随意运动的协调。②皮质核束是由运动皮质发出的纤维直接或间接止于脑神经核（Ⅲ、Ⅳ、Ⅵ、Ⅶ和Ⅹ等）组成的传导束。

（五）神经系统对内脏功能的调节

1. 外周神经对内脏功能的调节

（1）机体的内脏活动受交感神经系统和副交感神经系统的调节。交感神经和副交感神经在起源，走行，换元，节前节后纤维长度及比例及分布等均有差异。

（2）神经递质和受体 副交感神经节后纤维末梢释放的递质为乙酰胆碱，同内脏器官细胞膜上的M受体结合后发挥作用。交感神经节后纤维（除支配汗腺和骨骼肌的舒血管纤维外）末梢释放的递质为去甲肾上腺素。

能与去甲肾上腺素结合的有α和β两种受体。α₁受体分布于大多数内脏和血管平滑肌以及腺体；α₂受体分布于小肠平滑肌。β受体又分为β₁、β₂、β₃受体，β₁受体分布于心肌组织；β₂受体分布在支气管、胃肠和子宫平滑肌以及骨骼肌和心脏的血管平滑肌；β₃受体分布在脂肪细胞。不同的受体兴奋或同一类受体兴奋后，可表现为复杂的功能活动变化。

（3）交感神经和副交感神经对内脏功能调节的特征

①紧张性作用②相互协同的作用，交感和副交感神经的活动可表现为协同作用③既对立又统一的作用，对接受交感和副交感双重神经支配的同一组织或器官，两种神经的作用往往是相互对抗的。这种对抗作用使自主神经系统从正反两个方面调节内脏的活动，有利于机体内环境的稳定。交感神经活动常伴有肾上腺髓质激素的分泌增加，这一功能系统称为交感-肾上腺髓质系统。在创伤、恐惧和剧烈运动时，该系统的作用占优势，有利于调动体内潜力以适应体内外环境的急骤变化。副交感神经活动常伴有胰岛素分泌增加，称为迷走-胰岛素系统，该系统通过促进体内的消化和吸收以及合成代谢等活动，有利于对整体功能进行保护。在机体处于安静状态时，迷走-胰岛素系统作用占优势。

2.中枢神经系统对自主性功能的调节

（1）脊髓对自主性功能的调节

在脊髓内有血管反射、排尿和排便以及发汗等的初级中枢。

（2）低位脑干对自主性功能的调节

延髓是生命活动的基本中枢。

3.下丘脑对自主性功能的调节

下丘脑是内脏活动的整合中枢，主要作用是通过对摄食、体温和水平衡等的调节，将内脏的活动同其他功能结合在一起，形成完善而精确进行的整体功能。

（1）对摄食活动的调节，摄食活动由下丘脑、大脑边缘叶和大脑皮层共同调节，其中下丘脑是最基本和最重要的中枢。与摄食活动有关的中枢包括摄食中枢和饱中枢（2）对饮水活动的调节，下丘脑外侧区有渴觉中枢，同时，下丘脑视上核分泌的抗利尿激素可促进肾远曲小管和集合管对水的重吸收。（3）对机体产热和散热的调节，视前区-下丘脑前部和后部分别有对血温升高和降低敏感的神经元，体温调节的整合中枢亦位于下丘脑。（4）对情绪反应时内脏活动的调节，在下丘脑外侧区和腹内侧区有愉快或痛苦的中枢，以及参与机体防御反应的中枢，这些部位调节机体情绪反应时的内脏活动变化。（5）对垂体功能活动的调节， 下丘脑的视前区、腹内侧核和弓状核等部位，存在大量的神经内分泌细胞，其中的肽能神经元能分泌多种具有调节腺垂体功能活动的多肽，称为下丘脑调节肽，这些肽类物质经轴浆运输至正中隆起，然后释放入垂体门脉系统，转运至腺垂体的相应靶细胞，调节其分泌活动。下丘脑视上核和室旁核的神经内分泌细胞合成的血管升压素和催产素，经下丘脑－垂体束运至神经垂体储存，下丘脑可控制其释放（6）对生物节律的控制，体内的自主活动按一定的时间顺序、周而复始地有节律地发生和变化，称之为生物节律。目前认为，控制生物节律的中枢在下丘脑的视交叉上核以及同其相联系的松果体和垂体等部位，它们共同组成松果体-下丘脑-垂体节律系统，负责控制和协调体内功能活动的时序性和节律性。

4.大脑皮层对自主性功能的调节

大脑新皮质和边缘系统是调节内脏活动的高级中枢。通过整合来自各级内脏调节中枢和各种内脏反射的信息，进而对心血管、呼吸、消化、排泄、产热和散热以及性活动等进行精确的调节，并使体内各种内脏活动相互协调以同整体功能状态保持一致。

（六）脑的高级功能

1.大脑皮层的电活动  包括自发脑电活动和皮质诱发电位两种。

（1）在安静时，大脑皮层经常具有持续的节律性电位变化，称为自发性脑电活动。脑电图根据其频率、振幅和特征的不同有α、β、θ、δ四种基本波形。

（2）皮质诱发电位是指刺激特定感受器或感觉传入神经时，在大脑皮层相应区域引出的电位变化。

2.觉醒和睡眠

觉醒和睡眠是人和高等动物生命活动中所必需的两个相互转化的生理过程。

（1）根据整体功能和脑电图的变化，可分为行为觉醒和脑电觉醒两种状态。前者对各种新异刺激具有发生探究性行为的能力，后者仅表现为觉醒时的脑电图变化。觉醒的产生机制与丘脑感觉的非特异性投射系统以及某些中枢核团的活动同觉醒产生有关。

（2）睡眠有慢波睡眠和快波睡眠两种不同的时相状态。慢波睡眠和快波睡眠及相互交替。

3.学习和记忆

学习是人类和其他动物的神经系统不断接受环境信息而获得新的行为习惯的过程。各种条件反射的建立，就是一种简单的学习和记忆的过程。在学习过程中，通过感觉器官对外界事物认识之后，即使感知的事物不再作用于感官，事物在脑中的印象也可保持相当长的时间，并在某种条件下这种印象被再现出来，称为记忆。学习是记忆的前提，记忆是学习的结果。

学习主要分为非联合型学习和联合型学习两类。

记忆过程可分成四个连续的阶段，即感觉性记忆、第一级记忆、第二级和第三级记忆。前两个阶段为短时记忆，后两个阶段为长时记忆。

遗忘是记忆的对立面。常见的有顺行性遗忘和逆行性遗忘。

4．大脑皮层功能的不对称性

对语言和非语言方面的调节活动中，左、右半球又各具优势而表现出功能的不对称性。左半球在语言功能上占优势，称之为优势半球或主要半球，称右半球为次要半球。但在某些高级神经活动方面，左右半球各有其高度专门化的功能。相对而言，左半球在语言功能上较右半球占优势，右半球在非语词性认识功能上较左半球占优势。